The present invention relates to a battery pack and a thermostat used therefor, and particularly to a technical field of a battery pack in which a battery cell and a circuit board for protecting the battery cell are housed in a casing, and a thermostat used therefor.
There is a battery pack, for example a battery pack in which a lithium ion secondary battery cell is housed in a casing. Such a battery pack is used as a power supply for a communication apparatus such as a portable telephone, for example.
FIG. 7 and FIG. 8 schematically show an example of a conventional battery pack.
A battery pack “a” is formed by housing a battery cell “c” such as a lithium ion secondary battery cell or the like and a circuit board “d” for protecting the battery cell “c” within a casing “b”. The battery cell “c” is formed by sealing a battery main body portion “e” with a covering (aluminum laminate material) “f” made of a polymer material.
A first electrode lead “g” connected to a positive electrode of the battery cell “c” and a second electrode lead “h” connected to a negative electrode of the battery cell “c” are projected from the battery cell “c” in the same direction in a state of being separated from each other at a distance in a direction of width of the battery cell “c”.
The circuit board “d” is provided with a first electrode connecting portion “i”, a second electrode connecting portion “j”, and thermostat connecting portions “k” and “k”. An end portion of the first electrode lead “g” projected from the battery cell “c” is connected to the first electrode connecting portion “i”. An end portion of the second electrode lead “h” projected from the battery cell “c” is connected to the second electrode connecting portion “j”.
The circuit board “d” has a thermostat “l” mounted thereon to prevent excessive increase in temperature within the casing “b”. The thermostat “l” has a casing portion “m” formed of a nonconductive material, and a pair of electrode portions “n” and “n” projected from the casing portion “m” in directions opposite to each other. The electrode portions “n” and “n” are joined to the thermostat connecting portions “k” and “k”, respectively, of the circuit board “d” by soldering, for example. The thermostat “l” is situated immediately beside the first electrode connecting portion “i”.
The circuit board “d” has required chip parts “o”, “o”, . . . such as ICs (Integrated Circuits), FETs (Field Effect Transistors), and the like mounted thereon.
However, the conventional battery pack “a” described above requires the thermostat connecting portions “k” and “k” exclusively for connecting the thermostat “l” to the circuit board “d”, in addition to the first electrode connecting portion “i” and the second electrode connecting portion “j”. Hence there are a correspondingly large number of components on the circuit board “d”.
In addition, the thermostat “l” needs to be mounted at a position different from positions of the first electrode connecting portion “i” and the second electrode connecting portion “j” of the circuit board “d”. Accordingly a space exclusively for mounting the thermostat “l” on the circuit board “d” is required, so that with an increase in size of the circuit board “d”, the battery pack “a” becomes larger.
It is accordingly an object of the present invention to provide a battery pack and a thermostat used therefor that overcome the above problems to reduce components of the circuit board and miniaturize the battery pack using the thermostat.